The constitutive response of a commercial magnesium alloy rolled sheet (AZ31B-O) is studied based on room temperature tensile and compressive tests at strain rates ranging from 10
−3
to 10
3
s
−1
. Because of its strong basal texture, this alloy exhibits a significant tension–compression asymmetry (strength differential) that is manifest further in terms of rather different strain rate sensitivity under tensile versus compressive loading. Under tensile loading, this alloy exhibits conventional positive strain rate sensitivity. Under compressive loading, the flow stress is initially rate insensitive until twinning is exhausted after which slip processes are activated, and conventional rate sensitivity is recovered. The material exhibits rather mild in-plane anisotropy in terms of strength, but strong transverse anisotropy (
r
-value), and a high degree of variation in the measured
r
-values along the different sheet orientations which is indicative of a higher degree of anisotropy than that observed based solely upon the variation in stresses. This rather complex behaviour is attributed to the strong basal texture, and the different deformation mechanisms being activated as the orientation and sign of applied loading are varied. A new constitutive equation is proposed to model the measured compressive behaviour that captures the rate sensitivity of the sigmoidal stress–strain response. The measured tensile stress–strain response is fit to the Zerilli–Armstrong hcp material model.
In recent years magnesium alloy sheet products have been attracting more attention because of their potential applications as coverings of portable electrical devices and automotive panels e.g. rocker and quarter panels. However, magnesium alloy sheets are usually formed at high temperatures because of their poor formability at room temperature, which requires a more complex tooling system. In this paper, a finite element model for deep drawing of AZ31 alloy sheet is developed, in which a 3-parameter Barlat plasticity yield surface is adopted. Material behaviour including yielding stresses and anisotropic coefficients are measured from the experiments performed at elevated temperature on a partially annealed AZ31 alloy sheet. Finite element model used in this research is a coupled thermo mechanical model. The commercial finite element code, LS-Dyna, was used for this purpose. Correspondingly warm forming experiments are performed and the results are used to validate the results of the model.
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